Investigations have been carried out at Centralne Laboratorium Gazownictwa (Central Laboratory of Gas Industry), Warsaw, on catalytic methods for destroying phenols and other impurities in vaporized strong phenolic effluents. The first studies were made on standard solutions of phenols and ortho-cresol in concentrations of about 5000 mg/l and on much more concentrated solutions in which the content of phenol and ortho cresol was about 45,000 mg/l. Afterwards, crude effluents coming from coke ovens of various types e.g. Didier, Glover West, Koppers, as well as from the “Viag” gas producer, were examined, as were condensates from coke oven gas mains, and some effluents from tar processing plant. The results of the investigations showed that in the presence of catalyst, phenols can be completely oxidized by air. It was found also that some other impurities-for example ammonia, hydrogen sulphide, hydrogen cyanide, etc.-usually accompanying them in the effluents, were simultaneously oxidized to neutral substances like CO 2, N 2, H 2O, NO 3 −, SO 4 2−. The process must be carried out on evaporated effluents in the presence of a copper catalyst and about 3 per cent of air. The mixture must be superheated to a temperature of 300–400° C at atmospheric or higher pressure. The process requires a temperature of over 1000° C if phenols are to oxidize completely without the use of a catalyst. In effluents, such substances as ammonia and hydrogen sulphide have the greatest adverse effect on the oxidation but hydrogen cyanide has less influence on it. By the above method, in contrast to others, about 90 per cent of impurities from crude effluents are oxidized, and the final product is pure water. About 10 per cent of impurities remains in the apparatus as a tar sludge which can be easily burned in a steam-boiler, or utilized in other ways; for example it can be mixed with coal tar. The water derived from the effluents during the process is a clear condensate which is suitable as make-up water in cooling systems to decrease salinity. The economic interest of this method lies in the possibility of using the steam for water gas production or for damping the blast air for gas generators. Alternatively, it can be used as a source of heat in the effluent purification process. It will be seen that when phenolic effluents are treated by this catalytic method all the impurities are removed, whereas other methods, such as treatment by chlorine dioxide, nitric acid, chlorinated lime or sulphur dioxide, leave a residue in the treated effluent. Moreover these latter methods require an excess of reagent, which remains in the effluent whereas in the catalytic method only a slight excess of air is required.